Acariasis is a group of conditions caused by mites, mostly flour mites.


Causes

Mites are oval in shape, 100 - 500μm in size, mostly as white as dust, often with numerous long hairs on the body surface.

Flour mites appear in the form of eggs, larvae, protonymphs, deutonymphs, tritonymphs, and adults in their different developmental stages. When the condition is unfavorable, deutonymphs are often stationary and adhered to other arthropods. Sometimes, deutonymphs are absent, and protonymphs develop directly into tritonymphs.

Figure 1 flour mites

Flour mites often reproduce in spring and autumn. After humans are bitten by the flour mites in the air, dermatitis occurs and is manifested by erythema, papulovesicles, and pustules. Skin lesions can fuse together, which may be related to the saliva composition of flour mites. Some flour mites can contaminate skin wounds, resulting in protracted duration.

If the flour mites in dust are inhaled into the lungs, although most of them can be spit out with the sputum, small amounts of flour mites remain in the lungs, causing a non-specific inflammatory reaction, termed pulmonary acariasis. Flour mites and their eggs can be detected in the sputum.

Flour mites that live in dried fruits and other foods can be swallowed. They migrate through the stomach and small intestine, and finally stay in the large intestine to reproduce and destroy the intestinal wall tissue, leading to intestinal wall ulcers, termed intestinal acariasis, mainly in summer in the tropical and temperate zones. Live mites and their eggs can be found in fecal examinations.

Flour mites can also invade the urinary tract and cause urinary acariasis. Flour mites can be detected in the urine from patients with nephritis, especially children. Flour mites may be detected in the cerebrospinal fluid in patients with cranial nerve symptoms as well.

The secretions, excretions, and carapaces of live mites and cleavage products of dead mites are strong allergens, which can cause allergic reactions such as urticaria, rhinitis, and asthma.


Signs and Symptoms

Cutaneous acariasis

The clinical manifestations are erythema, papules, and pustules, followed by exfoliation, eczema, and even pyoderma occasionally.

Pulmonary acariasis

Pulmonary acariasis is mainly manifested by cough, chest tightness, chest pain, asthma, shortness of breath, low-grade fever, fatigue, night sweats, bloody sputum, and hemoptysis. Hilar shadow augmentation can be seen in pulmonary x-ray examinations.

Intestinal acariasis

Symptoms include abdominal pain, diarrhea, loose stools, mucus in stools, burning sensation in the anus, fatigue, emaciation, and lassitude, and can last for several months.

Urinary acariasis

The main clinical presentations are nocturnal enuresis and urinary tract irritation symptoms, such as frequent urination, urgency, dysuria, abnormal urine volume, and proteinuria, as well as pyuria and hematuria in some patients. There may be fever, renal region pain, and percussion tenderness.

Allergy

Allergic asthma is very common.


Diagnosis

If there are clinical manifestations and isolation and identification of mites from the skin lesions, feces, sputum, or urine, the disease can be definitively diagnosed.


Treatment

Cutaneous acariasis can be treated by sulfur ointment or naphthol sulfur ointment.

Pulmonary acariasis is treated with metronidazole 600mg in 3 divided doses or 800mg in 2 divided doses for 7 days followed by an interval of 7 - 10 days without treatment, repeated twice. If the symptoms cannot resolve, praziquantel 25mg/(kg·d) orally in 3 divided doses can be considered.

Urinary acariasis can be treated by chloroquine, metronidazole, and ivermectin.

Desensitization treatment can be applied to patients allergic to mites.